We wish to examine the expression and function of the BLV LOR region. The expression of the LOR region will be studied by Northern blot analysis of FLB associated tumors using probes derived from LOR region subclones. The mRNA will be characterized using S1 nuclease mapping and sequencing of the LOR region cDNA clones. To identify potential protein products encoded by this region we plan to use in vitro translation of hybrid selected messages, raise antisera to synthetic peptides and express this region in bacteria using open reading frame vectors (ORF). Functional analysis of the LOR protein products will be achieved by either microinjection of LOR protein or expression of the LOR region in eukaryotic cells. Finally, we plan to examine the effect of LOR region deletions on virus replication and in vitro immortalization abilities.